Radiological hazard assessment and investigation of heavy minerals of economic importance in Mwita Syano river bed sands.

Abstract

Heavy minerals are important economic resources as they are useful in many industrial applications such as manufacturing of tiles and pigments. Even though heavy minerals are of great value, studies have shown that some minerals such as monazite which contain thorium, a radioactive element, and therefore heavy minerals may be a source of gamma radiation. Therefore, the main aim of this research was to investigate heavy minerals of economic importance and also to assess radiological impact of the heavy mineral sands in Mwita Syano River bed sands. The radiological impact was investigated using high purity germanium spectrometer while heavy mineral assessment was analysedusing Xray Powder Diffraction spectrometer. The result showed that the activity concentration of 226 Ra varied between 4.52 Bq kg-1 and 35.7 Bq kg-1 with an average of 13.45 Bq kg-1 while 238U ranged from 3.12 Bq kg-1 to 47.3 Bq kg-1 with an average of 8.12 Bq kg-1. Specific activity of 40K on the other hand varied between 111 Bq kg-1 and 459 Bq kg-1 with an average of 321 Bq kg-1 while the annual effective dose ranged between 0.0136- 0.0787 mSv yr-1 with a mean of 0.031 mSv yr-1. On the other hand XRD analysis showed that the only available heavy mineral of economic importance is magnetite which had an average percentage of 0.15 %. However, other valuable minerals such as albite and orthoclase were also found in the sands and they had an average percentage of 23.46 % and 4.67 % respectively. In conclusion therefore, the average specific activity of these sands are below the World averages hence they are not of radiological concern. The presence of magnetite, albite and orthoclase minerals indicate that there is a possibility that other heavy minerals could be present and therefore further analysis should be done on these sands. This is because heavy minerals are dense and therefore there is a possibility that they could have settled deeper into the ground.